Infectious disease & CDI Flashcards
Definition of Acute Infectious Disease
Acute: Increased freq of defecation lasting < 14 days
Diarrhoea: >= 3 loose/liquid stools OR
More frequent than normal
- Caused by 1/more micro-organisms
LO1: Microbiology of Acute Infectious Disease
1) Bacterial
- C.difficle, Vibrio cholera, E.coli, Shigella spp,
Salmonella typhi, Campylobacter jejuni
2) Protozoal
- Giardia intestinalis, Entamoeba histolytica, Cryptosporidium parvum
3) Viral (Most common)
- Noravirus, rotavirus, adenovirus
Methods to diagnose Acute Infectious Disease
1) Fecal occult blood - Non-specific, look for blood
in stools
2) Ova & parasite - By microscopy
3) Stool cultures - Takes few days, so not commonly done
4) PCR - More rapid, can look for multiple targets @ once
Quite ex
Who are diagnostic tests for Acute Infectious Diseases reserved for?
- Severe illness
- Persistent fever
- Bloody stools
- Immunosuppression
- Unresponsive to treatment
- Usually not indicated, most cases are self-limiting
How to prevent Acute Infectious Diseases?
1) Good hand & food hygiene practices
2) Vaccinations
- For travellers to endemic areas: Cholera, typhoid
- 6months-5y/o: Rotavirus
Treatment of Acute Infectious Diseases
Non-pharmacological:
- Early re-feeding as tolerated
- Easily digestible food (eg. cereal, bananas)
Pharmacologic
- Self-care: Oral rehydration therapy, anti-peristaltics, adsorbents, probiotics
- Antibiotics (for PR3124) [MOST cases self-limiting]
Indications for antibiotics for Acute Infectious Diseases
1) Severe disease
- Fever with bloody diarrhoea/ mucoid stools/ severe abdominal pain
2) Sepsis
3) Immunocompromised
Clinical benefits of antibiotics for Acute Infectious Diseases
1) Decrease duration of symptoms (1-2 days)
2) Decrease morbidity & mortality
Antibiotic regimen for Acute Infectious Diseases
1) IV Ceftriaxone 2g Q24h
2) PO Ciprofloxacin 500mg BD (if can’t tolerate B-lactam)
Duration of therapy: 3-5 days
- May be extended in bacteremia/ extra intestinal infections/ immunocompromised
- Rarely need to think about stepping down to PO
What is Clostridioides difficile?
- Gram (+), spore-forming anaerobic bacillus
- -> Produces toxins A & B
- Most common cause of nosocomial diarrhoea
- Increases duration of hospitalization & healthcare cost
How is Clostridioides difficile transmitted?
- Fecal-oral route
- Contaminated environmental surfaces
- Hand carriage by healthcare workers
(Often within hospital envt, C.diff form spores hence infected persons can be asymptomatic)
Pathogenesis of Clostridioides difficile
- Normal gut flora is altered by broad-spectrum antibiotics
- C. difficile contains endospores that can survive acidity of stomach & reach the large intestine
- C. difficile flourishes in colon, produces toxins A & B that cause mucosal damage
- -> Bleeding, symptoms of C. difficile like fever, crampy abdominal pain, diarrhoea
Risk factors for C. difficle
1) Healthcare exposure
- Prior hospitalisation
- Duration of hospitalisation
- Long-term care facilities/ nursing homes
2) Pharmacotherapy
- Systemic antibiotics (no. of agents, duration)
- High risk Abx: Clindamycin, fluoroquinolones
2nd gen Cephalosporins
- Use of gastric acid suppressive therapy
(Easier for spores to get into colon)
3) Patient-related factors
- Multiple/severe comorbidities
- Immunosupression
- Advanced age > 65yo
- History of CDI (May have recurrence)
Clinical presentations of C. difficile
1) Mild
- Loose stools, abdominal cramps
2) Moderate
- Fever, nausea, malaise
- Ab cramps & distension
- Leukocytosis
- Hypovolemia
3) Severe/fulminant (rare but serious)
- Eg. ileus, toxic megacolon, pseudomembrance colitis, perforation, death
Process of diagnosis for C. difficle
1) Clinical suspicion (Don’t have to be hospitalised/ on antibiotics)
- Unexplained + new onset of diarrhoea (ie. >= 3 unformed stools in 24hrs) OR
- Radiologic evidence of ileus/ toxic megacolon
2) Confirmatory test/ finding
- (+) stool test result for C.difficle/ its toxins OR
- Histopathologic findings of pseudomembranous colitis
Diagnostic tests for C. difficile
1) Nucleic acid amplification test (NAAT)
- i) Toxin enzyme immunoassay (EIA): Looks for toxin A/B
- ii) Glutamate dehydrogenase (GDH) EIA:
Looks for enzyme
2) PCR
(Both have fast turnaround)
- Cultures not routinely performed due to long turnaround time
- Do not test asymptomatic patients
(Based on clinical suspicion) - Do not repeat testing in < 7 days (waste time & money)
- Do not perform test of cure
–> Only monitor resolution of symptoms, don’t need to ensure clear of C. diff
Infection control of C. difficile
Healthcare setting:
- Practice hand hygiene
- Contact precautions recommended for 48hrs after diarrhoea resolves (gloves, gown, wash hands with soap & water)
At home:
- Wash hands with water & soap after bathroom
- Use separate bathroom if possible
- Clean toilets, linens, towels, clothing with bleach
When to recommend empiric CDI treatment?
1) Fulminant CDI
2) Substantial delay (>48h) in diagnostics
Antibiotic regimen for C. difficile (1st episode)
Non-Severe (WBC < 15, SCr < 133):
i) PO Vancomycin 125mg QDS or
ii) PO Fidaxomicin 200mg BD
(Alternative) PO Metronidazole 400mg TDS
Severe (WBC >= 15, SCr >= 133):
i) PO Vancomycin 125mg QDS or
ii) PO Fidaxomicin 200mg BD
Fulminant (Hypotension/ Ileus/ Megacolon):
i) IV Metronidazole 500mg Q8h +
PO Vancomycin 500mg QDS
(+/-) PR Vancomycin 500mg QDS
Duration: 10 days (May extend to 14 if symptoms not completely resolved)
Why is Metronidazole still used locally?
- Cost & logistic consideration
(PO Vanco is prepared by compounded IV form to oral syringes) - Avoid repeated/prolonged courses
Benefits & Drawbacks of Fidaxomicin
- Narrow spectrum
- Lower MIC vs Metronidazole/Vancomycin
- Significant PAE
- Less alteration of normal gut flora
- May improve cure in immunocompromised patients
HOWEVER…
- $$$
- Hence, limited to severe &/or recurrent cases non-responsive to max standard therapy
Antibiotic regimen for C. difficile (Recurrence)
1st recurrence:
[Metronidazole initially]: PO Vanco 125mg QDS x 10days
[1st line initially]: PO Vanco taper/
PO Fidaxomicin 200mg BD x 10days
2nd/subsequent recurrence:
i) PO Fidaxomicin 200mg BD x 10days
ii) PO Vancomycin taper
iii) PO Vancomycin 125mg QDS x 10days,
followed by Rifaximin 300mg TDS x 20days
iv) Fecal microbiota transplant
Monitoring of C. difficile therapy
- Clinical improvement: ~ 5-7days
Do not continue C. difficle for concurrent antibiotics:
- -> Assess for indication to continue systemic
- Stop systemic –> C. diff Abx –> Continue systemic
- SERIOUS (eg. DFI): No choice, use concurrently
Probiotics (Role, guidelines)
Contain: Saccharomyces boulardii/ Lactobacillus spp
Proposed mechanism: Maintain/restore healthy gut flora
Guideline recommendations:
- Not recc for routine use to prevent/treat CDI
- No harm to try unless immunocompromised
Role of Anti-mobility agents?
Eg. loperamide, atropine, diphenoxylate
To provide symptomatic relief for diarrhoea by inhibiting contraction of intestinal smooth muscle
- Limited role in infectious diarrhoea
